Here's Why Running Makes You Poop

If You've Ever Had to Go Number 2 on a Run, Here's Why — and How to Avoid It

If you've ever been midway through a run and experienced a familiar, need-a-bathroom-right-now feeling in the pit of your stomach, you're not alone. That dire need to go "number two" is what's known as runner's trots, and it's led to the tried-and-true tradition of plotting running routes with bathroom stops. That's great when it works, but it's still not ideal to stop mid-run to hit up a public bathroom, and there's not always one around right when you need it. So what actually causes runner's trots and, more importantly, is there any way to prevent it? We talked to Linda Nguyen, MD, a gastroenterologist at Stanford Health Care, to find out.

Why Does Running Make You Poop?

Runner's trots happens because strenuous exercise (like running) triggers a response from your sympathetic nervous system, Dr. Nguyen told POPSUGAR. Your SNS is a part of your autonomic nervous system, which controls bodily functions that you don't have control over, like the beating of your heart, sweating, and digestion. The sympathetic nervous system is also called your "fight or flight" response, and revs your body up "when you're under stress," Dr. Nguyen explained, like during intense exercise such as running. That response can also affect your digestion, increasing motility (the contraction of muscles within your gastrointestinal tract) and leading to diarrhea.

The more strenuous the run, the worse your symptoms can be. "Marathon running is associated with more GI issues than a slow, casual jog," Dr. Nguyen said. Studies have actually shown that extremely long runs such as marathons force your body to redirect blood from the gastrointestinal (GI) tract and send it to your muscles. That can be an issue, because "you need blood flow to the gut to digest and break down food," Dr. Nguyen said. Without it, your digestion can be affected, causing GI distress.

How to Prevent Runner's Trots

Not eating before a run can help you avoid the urge to poop, Dr. Nguyen said. If you're running for longer than an hour, though, you'll probably need a snack beforehand to keep your energy up. When that's the case, Dr. Nguyen had a few recommendations.

First, she said, avoid foods like:

Dairy

Fruits and juices

Onions

Garlic

Sugary foods or foods with artificial sweeteners

Basically, you want to avoid eating FODMAP foods. FODMAP is an acronym that stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, all ingredients that Dr. Nguyen said can cause GI distress before a run, especially if you struggle with irritable bowel syndrome.

If you're dealing with the urge to go number two on a run, Dr. Nguyen said there's really not much you can do but head for the nearest bathroom. If it's happening on a regular basis, try changing your prerun snack or going without food, if the run isn't too long. Stress can also cause GI issues on a run, Dr. Nguyen added; think of the flood of stomach-churning nerves you get before a race. If that's the case, she recommended meditation, deep breathing, or antispasm medication, which can calm your gut and relieve cramps. For a non-prescription solution, you can drink peppermint tea or take peppermint oil.